The invention relates to a digital solid-state trip unit for an electrical circuit breaker. The development of microprocessors has enabled digital techniques, whose reliability and scope for adjustment and adaptation to a large number of functions are well known, to be implemented in electrical circuit breaker trip units. The circuit breakers are adapted to the type of protection and to the installation protected and it is advantageous to be able to meet the different requirements with a single equipment item, notably with a single trip unit, which is customized when assembly has been completed or if possible when it is installed.
The object of the present invention is to enable a trip unit fitted with optional functions to be produced.